Probably should have added this in the first post.....
I have 2 bad knees one was a meniscus torn in 2 places (no surgery, just let it wear in which was an option recommended by the MD) which put me in a brace and on crutches and a cane for a long time. The other most definitely had a rather bad bruise to the joint and possible meniscus which put me in a brace and on a cane for a few months. The one with the diagnosed tears is now arthritic and I have had Cortisone shots in both. Stopped my Xingyiquan because of this, the knees could not take it, even with proper stance. That was my problem
I was concerned about Gee Kim Yeung Ma and my knees because of prior injuries and early on (first 2 classes) after what amounted to a half hour standing in Gee Kim Yeung Ma my knees felt strange and made me think that I would be limping the next day and that had me concerned. But the next day, much to my surprise, they were great and actually felt stronger.